/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
        if(root1==null||root2==null){
            return root1==null?root2:root1;
        }
        return Merge(root1,root2);

    }
    TreeNode Merge(TreeNode root1,TreeNode root2){
        if(root1==null||root2==null){
            return root1==null?root2:root1;
        }
        root1.val+=root2.val;
        root1.left=Merge(root1.left,root2.left);
        root1.right=Merge(root1.right,root2.right);
        return root1;

    }

}